Research shows the prevalence of obesity is increasing. The greatest increase occurs between 20 and 29 years of age. Obesity results from a long-term positive energy balance attributable to eating and exercise behaviors. Research shows effective behavior change interventions impact cognitive constructs which explain specific behaviors. Objectives were to develop and validate a weight-related behaviors questionnaire (WRBQ) for young adults with individual eating and exercise behavior scales and explore the impact of the scales to explain patterns of energy intake and exercise participation. The sample (N-721) consisted of 18 to 24 year old females (69.5%) and males (30.5%) with a mean age of 18.9 years (SD 1.1). Body mass index (BMI) was 23.1 kg/m² (SD 3.5) and 24% overweight or obese (BMI≥25.0 kg/m²). Selected test items were generated from a literature review and finalized by an expert panel. Factor analysis was conducted to explore and confirm the structure of the two scales. Validation analyses were performed by univariate statistics and structural equation modeling using BMI, percent dietary fat, fruit and vegetable intake, and moderate to vigorous-intensity activity. The WRBQ has 31 items with four eating and three exercise behavior constructs. Routine (RR) and Compensatory Restraint (CR) were associated with a dietary pattern of low energy density but RR was positively associated with BMI while CR had a negative association, particularly in females. External Eating (EX) but not Emotional Eating (EE) was associated with a dietary pattern of high energy density. The three exercise constructs explained a large portion of the variance in physical activity. Self-Regulation (SR) and Personal Barriers (PB) mediated the association between outcome expectations (OE) and physical activity. The WRBQ explains patterns of dietary intake and PA participation in young adults. Weight control interventions should focus on decreasing RR, EX, and PB and increasing SR.